One implementation of rotary storage involves storing sheets of media items (such as banknotes) around a rotatable drum. This is sometimes referred to as a rotary storage device.
In a rotary storage device, the drum is rotated, and either one or two tapes are wound around the drum. Media items are stored individually, either between successive windings of the tape (where one tape is used), or between two tapes (where two tapes are used) as those tapes are wound around the drum.
One advantage of such rotary storage devices is that the stored media items can be removed by reversing the direction of the tape or tapes. Such rotary storage devices provide a “first in last out” store for media items and can guarantee the order in which media items will be transported.
To ensure that media items are stored reliably, it is imperative that the tape is (or tapes are) always held in tension to ensure that there is no slack in the tape (or tapes). Any slack in the tape(s) could cause the tape to loop or become tangled. At best this would reduce the storage capacity of media items (because of the extra space taken up by the loop or tangle as it is wound around the drum). In some cases, this may cause the rotary storage device to jam (or the tape(s) to become tangled), thereby putting the device out of service until a service engineer repairs the device by unwinding (or cutting) the tape(s), removing media items stored on the tape(s), and then replacing the tape or tapes.
One way of maintaining tension on the tape(s) is to provide one motor for the storage drum and a separate motor for each tape reel used. However, this increases the cost of the rotary storage device.
It would be desirable to provide a rotary storage device that only uses one motor to drive both the drum and the tape reel(s), while maintaining the tape(s) in tension.